This invention relates to an improved molding composition. More particularly, this invention relates to a composition for making one-piece head molds and one-piece hand molds of living models.
Life-size, accurate replicas of body parts are used in a variety of fields, including art, medicine, and education. Materials that have been used for constructing molds for making such replicas suffer a number of drawbacks. For example, the consistency of most molding materials is not firm enough to adhere to vertical surfaces to which they are applied, such as is required in molding a head. These molding materials tend to slough or slide away in a mass from a vertical surface. Also, molding materials are usually not suitable for application directly to the skin because they stick after curing unless a coating of petroleum jelly or other separator is first applied to the skin. Another problem is that after curing, molding materials tend to become very rigid. For making one-piece head molds, a somewhat flexible material is needed to allow removal of the mold from the model without distortion of the mold. Further, the material should be applied as a single layer to make the mold as light as possible and to reduce the time the model must wait for the mold to cure. On the other hand, if the material cures too quickly the artist or technician may not have sufficient time to finish applying the material.
Alginate is a well-known material for making molds or for use in casting a replica. For example, dentists routinely use alginate for making impressions of teeth. As a casting material, alginate mixed with a filler, such as diatomaceous earth, sets to form a jelly-like object which dries to form a rigid object of smaller size that is a miniature of the jelly-like object (U.S. Pat. No. 3,958,997).
Alginate by itself suffers several drawbacks as a molding material for making one-piece head molds. Perhaps the most serious drawback is the difficulty of finding an alginate composition with a consistency that will permit application to vertical surfaces without sliding or sloughing off. Another drawback is that alginate tends to cure rapidly, making it difficult for an artist or technician to apply the material to an entire head in a single layer before it cures. If the alginate does cure before the application is complete, then additional layers may have to be applied to complete coverage, but layers of cured alginate do not adhere together very well and so a multiple layer mold made of alginate is impractical. Layers of alginate may be glued, but this is an inconvenient and time-consuming step. A further difficulty of using alginate alone to make molds is that cured alginate tends to sag and tear, especially when removing the mold from the model. Tears in the mold, of course, result in seam lines in the cast product. These seam lines require additional work to remove them in finishing the product.